This invention relates to a biomedical material and an artificial vessel, and in particular relates to a biomedical material for improving the adhesion and proliferation of cells and a modified artificial vessel.
Since PU (polyurethane) material has good mechanical property and bio-compatibility, it is widely used as a tissue substituent. However, it""s hard for cells to adhere onto the PU surface, let alone proliferate thereon. Therefore, the application of PU in tissue reconstruction, such as tissue repair, is limited.
For example, during the development of artificial skin or vessels composed of PU, the tissue cells (e.g. epithelial cells or endothelial cells) are usually first seeded on the surfaces of the PU material. In order to improve the adherence of cells on the PU material, the surfaces of the PU material have to be modified. One of the modification methods for the surfaces of the PU material is reactive graft, but the reaction conditions and the reproductivities are hard to control. Another method is to modify the surfaces of the PU material by plasma. However, the required plasma instruments are expensive, and each PU material has different structure and molecular weight, thus the period for plasma modification depends on various PU materials and tissue cells desired to attach and proliferate thereon.
It is easy and convenient to improve the attachment between the tissue cells and the biomedical materials consisting of PU by using adhering molecules consisting of protein or peptide. This method is based on the intracellular substance, which can regulate the adhesion, migration and growth of cells through the interaction with intergrins locating on the outer cell membranes. The adhering molecules of cells described above consist of proteins or peptides, which interact with intergrins locating on the outer membrane of cells. Therefore, these adhering molecules consisting of proteins or peptides can be used to enhance the attachment of cells. The amino acid sequences of these adhesion molecules all contain Arg-Gly-Asp (RGD), thus these adhering molecules are abbreviated as RGD-containing peptides or proteins.
Fibronectin is one of the natural RGD-containing peptides. Commercial fibronectin is very expensive because most of the commercial fibronectins are purified from plasma. Alternatively, RGD-containing peptides can be obtained by chemical synthesis or genetic engineering. However, chemical synthesis can only produce water-soluble RGD-containing peptides with low molecular weight (e.g. the peptide consisting of only six amino acids), which will associate with the intergrins and thus inhibit the attachment of cells. Therefore, it is necessary to develop a chemically immobilized peptide or high M. W. RGD-containing peptide.
Moreover, by using genetic engineering techniques, the high M. W. RGD-containing peptides or proteins can be mass-produced by microorganisms. A method for producing a chimeric protein, CBD-RGD, which contains a cellulose-binding domain (CBD), was disclosed by one inventor (David Chen) of this present invention [TW Patent Application No. 86114750 and U.S. patent application Ser. No. 09/166,966], wherein the gene encoding this CBD-containing chimeric protein was cloned into a vector to construct an expression vector. Then, this constructed expression vector was transferred into microorganisms, preferably E. coli., to mass-express the chimeric CBD-RGD containing protein encoded by this expression vector. Thus, a large amount of cheap CBD-RGD containing protein was recovered from the culture medium.
In accordance, in order to enhance the adhering ability and growing rate of tissue repairing cells on PU materials, this present invention discloses a novel tissue repairing biomaterial modified by the CBD-RGD containing peptide or protein produced according to the method disclosed in TW Patent Application No. 8611475 and U.S. patent application Ser. No. 09/166,966.
Moreover, the CBD-RGD containing peptide or protein can cooperate with cross-linked gelatin to modify the inner surface of the artificial vessel, and improve the adhesion and proliferation of endothelial cells on the inner surface of the artificial vessel. Also, the adhesion ability and the average degree of activation of platelets on the inner surface of the modified artificial vessel can be reduced.
This invention discloses a novel biomedical material, characterized by coating a genetically engineered CBD-RGD containing peptide layer on the surface of the biomedical material consisting of PU to improve the adherence of tissue cells on the biomedical material. Moreover, this invention discloses a modified artificial vessel, wherein the adherence of endothelial cells can be enhanced by coating a CBD-RGD containing peptide layer on the inner surface of the artificial vessels pre-modified by cross-linked gelatin. In addition, the adherence and activation of platelets on the modified vessel according to this invention can be reduced.
Other feature and advantages of the invention will be apparent from the following detailed description, and from the claims.